In step with downsizing and higher performance of electronic equipment, the packaging technique called the flip-chip method has recently received attention in order to satisfy demands for packaging of semiconductor parts at a higher density and an increase in the number of pins of each semiconductor part. The packaging using the flip-chip method is performed by forming salient electrodes (bumps) on electrode pads which are present on the surface of a semiconductor chip, and by directly joining the bumps to corresponding electrode pads on a substrate positioned to face the semiconductor chip. Using the flip-chip method is advantageous in that an area required for the packaging is substantially equal to the area of the semiconductor chip and the packaging can be achieved with a higher density. Further, the flip-chip method is suitably adaptable for an increase in the number of pins because the electrode pads can be arranged over the entire surface of the semiconductor chip. Still other advantages are that the length of each connecting wire is just required to cover the height of the bump electrode, thus ensuring good electrical characteristics, and that a surface of the semiconductor chip on the side opposite to a connected portion thereof is exposed, thus ensuring more efficient heat radiation.
In a flip-chip package, a resin is filled into a gap between the semiconductor chip and the substrate to reinforce the connected portion so that stresses generated due to the difference in thermal expansion coefficient between the semiconductor chip and the substrate are prevented from concentrating in the connected portion and breaking the connected portion. Such a process is called “underfill” (see FIG. 1).
The underfill process is performed by applying a liquid resin along an outer periphery (e.g., one or two sides) of the semiconductor chip, filling the applied resin into the gap between the semiconductor chip and the substrate by utilizing a capillary action, and by hardening the resin under heating in an oven, for example.
In the underfill process, a change in viscosity of the resin material over time has to be taken into consideration. This is because an increase of viscosity causes the problem that the amount of the resin material discharged through a material discharge port is reduced and the capillary action becomes insufficient, thus making the resin material hard to be filled into the gap in a proper amount. In the case of the resin material exhibiting a large viscosity change, a discharge amount of the resin material is reduced, for example, 10% or more after the lapse of 6 hours. This means the necessity of correcting the change in the discharge amount, which is attributable to the viscosity change over time.
Generally, a dispenser is used to fill the resin material in the underfill process. As one type of the dispenser, there is known a jet type dispenser which jets out small droplets of the liquid material through a nozzle.
A method of performing the underfill process by using the jet type dispenser is disclosed in, e.g., Japanese Patent Laid-Open No. 2004-344883 (Patent Document 1). More specifically, Patent Document 1 discloses a method of discharging a viscous material onto a substrate by using a jet type dispenser, the method including the steps of preparing a total volume of the viscous material to be discharged and a length over which the total volume of the viscous material is to be discharged, performing an operation to apply a plurality of viscous material liquid droplets onto a weight scale, generating a feedback signal representing the weight of the plurality of viscous material liquid droplets having been applied onto the weight scale, and determining a maximum relative speed between the dispenser and the substrate such that the total volume of the viscous material is discharged over the prepared length.
Also, Patent Document 1 discloses a method further including the steps of determining respective volumes of the plurality of viscous material liquid droplets, determining a total number of liquid droplets required to provide a volume substantially equal to the total volume, determining a distance between the liquid droplets, which is required to substantially evenly distribute the viscous material liquid droplets over the length, and determining a maximum relative speed between the dispenser and the substrate such that the total number of the viscous material liquid droplets are substantially evenly discharged over the length.                Patent Document 1: Japanese Patent Laid-Open No. 2004-344883        